KR101972688B1 - Method and apparatus for controlling the temperature of an injection valve - Google Patents

Abstract

The present invention relates to a method for monitoring the operation of a fuel injection system of an internal combustion engine, the method comprising the steps of: determining a threshold index for the thermal load of the injector of the fuel injection system; Checking if the determined threshold index is greater than a threshold value, checking whether the determined threshold index is greater than a threshold value for a predetermined period when the determined threshold index is greater than a threshold value, And if it is greater than the threshold value, introducing a measure to reduce the thermal load of the injector.

Description

Method and apparatus for controlling the temperature of an injection valve

The present invention relates to a method and apparatus for monitoring the operation of a fuel injection system of an internal combustion engine.

An internal combustion engine having a fuel injection system has already been known for a long time. Such an internal combustion engine is described, for example, in DE 10 2013 206 600 A1. In this publication, an injection system with one or more injection valves for injecting fuel into the internal combustion engine and a control method for such injection systems are described, wherein in the repeated injection cycle the closing element of the injection valve, At the actual-opening time OPP2, it is activated to collide with the upper stopper and / or to collide within the closed position at the actual-closing time OPP4, thereby producing a characteristic signal of the sensor element of the injection valve, A temporal signal profile of the sensor element is collected and a portion of the signal profile contained within the temporal search window of the injection cycle is examined and if the characteristic signal is not detected in the portion of the temporal signal profile described above, The retrieval process is executed in a subsequent injection cycle. This measure improves the reliability and robustness of the measurement of the opening and closing timing of the injection valve and, in addition, of the control method of the injection system.

There are ambiguous indications that, depending on the control of the operation of such internal combustion engines as described above, particularly with regard to regulating the amount of fuel using an injector driven in a piezo-electric manner, in some cases must be responsive to the situation.

The control unit of the internal combustion engine typically includes a plurality of control mechanisms and control circuits capable of raising or lowering the metered amount of fuel as needed. Some high control parameters are typically not important for low-dynamic motor operation, among other things. However, in order to avoid the possibility of a dangerous driving situation when the control parameters of the plural parameters have to be high and at the same time high-dynamic operation of the internal combustion engine, for example strong acceleration, has to be achieved, Care should be taken to ensure that the injector of the fuel injection system of the internal combustion engine is maintained within a stable operating range.

It is an object of the present invention to provide a method and apparatus for monitoring the operation of a fuel injection system of an internal combustion engine in which the injector of the fuel injection system can be maintained for as long as possible within a stable operating range during use of the internal combustion engine.

The problem is solved by a method having the features specified in claim 1 and by an apparatus having the features specified in claim 13. Preferred embodiments and improvements of the invention are set forth in the dependent claims.

The advantages of the present invention are, in particular, that by means of the claimed method, a safety function can be implemented which ensures that the injector of the fuel injection system is kept within a stable operating range for as long as possible. This reduces the likelihood of a dangerous driving situation, for example, that can occur during an overtaking process. Such a reduced situation may be achieved by first calculating and evaluating a criticality index from the parameters described above before introducing an appropriate countermeasure, if an increased value appears in a parameter important for the operation of the fuel injection system Within a response time of a certain degree and with which intensity the response measures should be introduced. This approach corresponds to variable error debouncing, depending on the instantaneous system conditions described by the parameters affecting the fuel injection system, in relation to the step size and the maximum value.

Further preferred features of the present invention will be apparent from the following exemplary description with reference to the drawings.
1 shows a block diagram for explaining the structure of a fuel injection system of an internal combustion engine,
Figure 2 shows a flow chart for explaining an embodiment of the method according to the invention,
Fig. 3 shows a block diagram for explaining a control unit of the fuel injection system of the internal combustion engine.

Fig. 1 shows a block diagram for explaining the structure of a fuel injection system 100 of an internal combustion engine. Such a fuel injection system 100 has a fuel tank 200 from which fuel is drawn by the fuel pump 300 through the fuel line 210. Within the fuel line 210, the fuel filter 220, shown in dashed lines, may be disposed. The fuel drawn from the fuel tank 200 by the fuel pump 300 is guided to the inflow valve 400 through the fuel line 310. The inlet valve 400 regulates the flow of fuel reaching the high-pressure pump 500 through the fuel line 410. The inlet valve 400 may be an integral component of the high-pressure pump 500. The compressed fuel in the high pressure pump 500 is delivered to the rail 600 through the fuel high pressure line 510. Starting from there, the fuel reaches the injector 700 through the high-pressure line 610 and the compressed fuel is injected into the combustion chamber of the combustion engine 800 through the high-pressure line. The rail 600 is connected to a digital pressure reducing valve 630, which may be an integral component of the rail. The digital pressure reducing valve 630 is connected to the fuel tank 200 via the fuel feedback line 620 to feed an excess amount of fuel from the rail 600 to the fuel tank 200 through the pressure reducing valve 630. [ . Alternatively, the fuel fed back through the fuel feedback line 620 may also be fed back to the fuel filter 220, as indicated by the dashed line in FIG. To collect the fuel pressure present in the rail 600, a pressure sensor 640 is provided.

Also, the fuel injection system 100 shown in Fig. 1 has a control unit 900 designed to control the injection process. The control unit 900 is connected to the inlet valve 400, the high pressure pump 500, the injector 700 and the pressure reducing valve 630 via a control line 910. [ The control unit 900 controls the injection process according to the instantaneous operating state of the internal combustion engine determined using the sensor signal, the stored table, and the stored operation program. The sensor signal includes a sensor signal s1 output by the pressure sensor 640, a sensor signal s2 output by the rotational speed sensor 810 and a sensor signal s3 output by the temperature sensor 820, ).

The control unit 900 uses the sensor signals provided to it, the stored table and the stored work program to determine the instantaneous output of the internal combustion engine, the instantaneous fuel temperature, the instantaneous energy demand of the internal combustion engine And the instantaneous injection duration of the injector. In this case, the control unit determines the instantaneous energy demand by evaluating the time point OPP2, which means the opening time of the injection valve, which is described by the instantaneous control variable of the OPP2-regulator. If the viewpoint appears relatively early in the injection cycle, there is relatively little energy demand momentarily. On the other hand, if the time point appears relatively late in the injection cycle, there is a relatively high energy demand momentarily. Further, the control unit uses the stored injection period characteristic map and evaluates the time points OPP2 and OPP4 to determine a momentary injection period. In this case, OPP4 is a closed state of the injection valve described by the control variable of the OPP4- Time.

Figure 2 shows a flow chart for explaining an embodiment of the method according to the present invention.

In this method, at step S1, a determination is made of a critical index (I) for the thermal load of the injector of the fuel injection system. When there is a large temperature gradient between the head spot and the foot spot of the injector housing, the heat load of the injector is high. In this case, the necessity to monitor the thermal load of the injector, and the necessity to check whether the injector can be maintained within a stable operating range under instantaneous thermal load, or measures should be introduced to reduce the thermal load of the injector.

For this purpose, in step S2 after step S1 in the embodiment shown in Fig. 2, inquiry is made as to whether the threshold index I determined in step S1 is larger than a preset first threshold value SW1.

If it is determined in the above checking step that the determined threshold index I is larger than the preset first threshold value SW1, it is determined in step S3 whether the determined threshold index I has already been set for the first predetermined period t1 It is inquired about whether it is larger than the first threshold value SW1 set in advance.

If it is determined in the inquiry process that the determined threshold index I is larger than the first threshold value SW1 already set in advance for the first period t1 set in advance, in step S4, an action for reducing the heat load of the injector Is introduced. Such a step belongs to the first reaction plane RE1. The action of the first reaction plane RE1 preferably involves reducing the number of active injections within one injection cycle. By reducing the number of active injections within one injection cycle of the injector, a reduction in the injector thermal load is achieved in a desirable manner such that the user can not sense or obscure the user.

If there is an internal combustion engine with an automatic transmission, instead of or in addition to reducing the number of active injections in step S4, automatic switching to a higher gear stage can be carried out. Automatic switching to such a higher gear stage also belongs to the action of the first reaction plane, does not limit the availability of the internal combustion engine and leads to a reduction in the injector thermal load.

On the other hand, if the result of the inquiry in step S2 indicates that the threshold index I determined in step S1 is smaller than the preset first threshold value SW1, then in step S5, the determined threshold index I is It is inquired as to whether it is larger than a preset second threshold value SW2 which is smaller than the preset first threshold value SW1.

If it is determined in the above inquiry process that the determined threshold index I is larger than the preset second threshold value SW2, it is determined in step S6 whether the determined threshold index I has already been set for the second predetermined period t2 It is inquired as to whether it is larger than the second threshold value SW2 set in advance.

If it is determined in the inquiry process that the determined threshold index I is larger than the second threshold value SW2 already set in advance for the second predetermined period t2, in step S7, an action for reducing the heat load of the injector Is introduced. Such a step belongs to the second reaction plane RE2. The action of the second reaction plane RE2 includes, for example, the number of revolutions and / or the torque of the internal combustion engine. The limit of the number of revolutions and / or the torque of the internal combustion engine as described above also reaches a situation in which the heat load of the injector is reduced in a preferable manner.

The action of the first reaction plane RE1 is particularly effective when the action of the first reaction plane RE1 does not limit or at best limit the momentary output of the internal combustion engine and is not as likely to the user's eyes, The action of the plane RE2 is different from the action of the second reaction plane RE2 in that it can limit the instantaneous output of the internal combustion engine to the extent that it can be sensed and can also be seen by the user.

Preferably, the predetermined first period t1 is smaller than the preset second period t2. Therefore, the action of the first reaction plane RE1, which is introduced when the determined threshold index I is larger than the first threshold value SW1 which is larger than the preset second threshold value SW2, The action of the second reaction plane RE2, which is introduced when the threshold index I determined to be different from the second threshold value SW2 is larger than the second threshold value SW2 but smaller than the first threshold value SW1, Is introduced only after elapsing.

The above-described threshold values SW1 and SW2 and the aforementioned periods t1 and t2 have been previously determined empirically by the vehicle manufacturer and stored in the memory of the control unit of the internal combustion engine.

The above measures for reducing the thermal load of the injector have already been previously assigned to the two reaction planes by the vehicle manufacturer and these assignments are likewise stored in the memory of the control unit of the internal combustion engine, .

If the result of the inquiry in step S5 indicates that the determined threshold index I is smaller than the preset second threshold value SW2, the process goes to step S8.

In this step S8, an inquiry about whether the determined threshold index I is smaller than a predetermined threshold value SW2 already in the preset third period t3, which is larger than the first period and larger than the second period, , And if so, the fact that the determined critical exponent (I) lies within its normal range is approved. In this case, the process goes to step S9. In this step S9, measures for reducing the heat load of the injector, which are introduced in accordance with the situation in step S4 or step S5, are called again (STOPPEN: stop). On the other hand, if it is determined in the inquiry process in step S8 that the determined threshold index I is not smaller than the previously set threshold value SW2 for the preset period t3, then in step S4 or step S5 The measures taken to reduce the heat load of the injector, which is introduced according to the situation, remain intact (WEITER: continue).

3 illustrates a control unit S of the fuel injection system of an internal combustion engine, designed to determine the threshold index I and to determine the triggering signals st1 and st2 for introducing measures to reduce the thermal load of the injector FIG. This control unit S is preferably a control unit 900 shown in Fig. 1 and provided for controlling the entire fuel injection system.

The control unit S is provided with a plurality of sensor signals s1 ... sn provided by respective associated sensors of the internal combustion engine. The control unit S evaluates the sensor signals using the work program stored in the memory SP and using another data stored in the memory SP and outputs the instantaneous output P of the internal combustion engine, , The instantaneous fuel temperature (T), the instantaneous energy demand of the internal combustion engine (E), and the instantaneous injection duration (T) of the individual injectors.

The parameters (P, T, E, and T) are variables that affect the temperature gradient that is dominant in the injector housing. Thus, for example, the instantaneous output P of the internal combustion engine is used as a measure for the combustion chamber temperature, nozzle heating and nozzle elongation. The instantaneous fuel temperature T is used, for example, as a measure for needle cooling and needle shortening. The high temperature gradients that appear along the injector body and also appear between the nozzle body and the nozzle needle are set especially when the induced output of the internal combustion engine is high. This situation corresponds to a high energy input from the combustion chamber into the interior of the nozzle, resulting in a high nozzle temperature. Further, when the fuel pressure is low, a large injection amount leads to combustion close to the nozzle. When the fuel temperature is low, excellent cooling of the nozzle needle is realized. This applies in particular when a long injection period is required, which is indispensable when the induced output of the internal combustion engine is high or when the fuel pressure is low.

Furthermore, the control unit S also evaluates the opening operation of the injector. Low energy demand indicates easy opening. Low OPP2-time indicates rapid opening. High OPP4-time indicates slow closure.

The above-mentioned parameters (P, T, E and T) are multiplied by a predetermined weighting factor stored in the memory (SP). The instantaneous energy demand E is then multiplied by the weighting coefficient k1 and the instantaneous energy demand E is multiplied by the weighting factor k2. , And the instantaneous injection period (T) is multiplied by the weighting factor (k4). These weighting factors were previously determined empirically and stored in the memory SP.

From the above parameters multiplied by the respective weighting factors, a threshold index I is determined by the addition process in the adder A:

P + k2

T + k3

E + k4

Τ.I = k1

P + k2

T + k3

E + k4

Τ.

The determined criticality index I is determined by a control unit S which determines the control signals st1 and / or st2 used to introduce measures to reduce the thermal load of the injector, using the determined criticality index I And is provided to the arithmetic unit R. [ In this case, if the control unit S approves the introduction necessity of the related measures in the control framework of the method described above with reference to Fig. 2, then the control signal st1 may indicate that one or more of the first reaction plane RE1 A plurality of actions are introduced and one or more actions of the second reaction plane RE2 are introduced by the control signal st2.

The above-described method is based on the fact that the operation of the piezo-driven injector is strongly dependent on temperature. In particular, the very high temperature of the injector body and the high temperature gradients along the injector body are factors that cause injector operation or injector control. Special focus also has to be fitted to the injector's insertion operation because in the case of a newly manufactured injector an accelerated characteristic change in the form of an open-circuit voltage drift may occur during the first operating time.

Typically, the injector is set such that, with respect to the material that constitutes the injector, the mutual thermal expansion of the individual injector components in the transient vibration state is generally compensated, resulting in the operation of the injector being stable over a wide temperature range. However, if the end area of the injector, for example the nozzle tip, is heated very quickly and strongly under certain motor operating conditions, the operation of the injector can reach its limit of stable working area.

Certain control interventions that exhibit no undesirable effects when the injector is fully heated in normal operation may cause problems in highly transient operation.

In order to avoid such problems and to be able to better evaluate the possible effects of the current operating state, in the above-described invention, an analysis of the kind of effect, in which the influence variables related to the thermal load of the injector are weighted and from which the critical exponent is determined effect chain analysis.

A high weighting factor implies a high impact of individual parameters on the criticality index, and vice versa.

The higher the criticality index, the more quickly it must respond to a particular error sign or symptom occurring in the injection system. A single high criticality index does not yet lead to a situation in which measures to reduce the heat load of the injector must be introduced. Only when a high criticality index exists for a predetermined period of time, an action is taken to reduce the thermal load of the injector. These measures increase the safety of error recognition and introduce appropriate countermeasures only when absolutely necessary.

In particular, the control unit (S) provided for monitoring the operation of the fuel injection system is configured to pre-set the period during which the critical exponent should exceed the individual threshold in accordance with the determined level of the critical exponent and also to reduce the thermal load of the injector The action (s) are also pre-set according to the level of the determined critical exponent, so that the result is always designed so that the appropriate response to the determined critical exponent can always be introduced.

Another advantage of the present invention is that in addition to the temperature transients that occur along the injector body during the highly transient operation or limit range operation of the injector, injector temperatures that are well above the pre-set operating temperature limits can also be collected . This high injector temperature can be set, for example, when the combustion chamber seal is defective.

In one preferred refinement of the invention, the slopes of these parameters as well as the instantaneous values of the abovementioned parameters are taken into account when determining the threshold exponent.

Claims (13)

CLAIMS 1. A method for monitoring operation of a fuel injection system of an internal combustion engine,
Determining a critical index (I) for the thermal load of the injector of the fuel injection system,
- checking whether the determined threshold index is greater than a threshold value (SW1)
- checking whether the determined threshold index is greater than a threshold value during a predetermined period (t1) if the determined threshold index is greater than a threshold value, and
Introducing an action RE1 for reducing the thermal load of the injector if the determined threshold index I is greater than a threshold value SW1 during a predetermined period t1,
Wherein a measure for reducing the thermal load of the injector is preset in accordance with the determined level of the critical exponent. The method according to claim 1, characterized in that the duration is preset in accordance with the level of the critical exponent. delete 2. The method according to claim 1, wherein a plurality of parameters to which the instantaneous induced internal combustion engine output (P), the instantaneous fuel temperature (T), the instantaneous energy demand of the internal combustion engine (E) Wherein a critical exponent is determined by evaluating the critical exponent of the fuel injection system. 5. A method according to claim 4, characterized in that said instantaneous energy demand (E) is determined by evaluating the time point (OPP2) of the injector. 5. A method according to claim 4, characterized in that said instantaneous injection duration (t) is determined by evaluating the time points (OPP2 and OPP4) of the injectors. 5. A method according to claim 4, characterized in that each of the parameters (P, T, E, t) is multiplied by a weighting factor (k1, k2, k3, k4) Way. 8. A method according to claim 7, characterized in that a threshold exponent is calculated by the operation of each weighting coefficient and the multiplied parameter. The method according to any one of claims 1, 2, and 4 to 8,
- checking whether the determined threshold index (I) is greater than a first threshold value (SW1)
If the check result is positive, it is checked whether the determined threshold index I is already greater than the first threshold value for a longer period than the first time period t1, and if so, the first reaction plane RE1, A step of activating an action of the user,
- checking if the determined threshold index (I) is greater than a second threshold value (SW2) smaller than the first threshold value if the check result is negative, and
If the check result is positive, it is checked whether the determined threshold index I is longer than the second threshold t2, which is already greater than the first period t1, and if so, , Activating the action of the second reaction plane RE2,
Wherein the action of the first reaction plane belongs to reducing the number of active injections. ≪ RTI ID = 0.0 > 8. < / RTI > delete 10. A method as claimed in claim 9, characterized in that, in the presence of an automatic transmission, an automatic transition to the higher gear stage belongs to the action of the first reaction plane. Way. 10. A method according to claim 9, characterized in that the action of the second reaction plane belongs to a limitation of the number of revolutions and / or the torque of the internal combustion engine. An apparatus for monitoring the operation of a fuel injection system of an internal combustion engine,
Characterized in that it comprises a control unit (S), characterized in that the control unit is designed to control a method having the features specified in any one of claims 1, 2 and 4 to 8, An apparatus for monitoring the operation of an engine fuel injection system.

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